1. Field of the Invention
The invention concerns a wedge drive or cotter key comprising a slider element receiving means, a movable slider element and a driver element, wherein sliding surfaces are provided between the slider element and the driver element.
2. Description of the Related Art
A wedge drive which is also referred to as a slider serves basically for diverting pressing forces to stamping or shaping tools in order thereby to be able to cut, perforate or shape in particular regions of bodywork portions, which are of an inclined or undercut configuration. In that arrangement the wedge drive includes at least one slider element receiving means, a movable slider element and a driver element. The slider element receiving means which as such as rigid is usually connected to a part of the press or the pressing tool, in which press or pressing tool the wedge drive is intended to implement the stamping or shaping operations. A wedge drive is referred to as an upper part slider if the slider element receiving means thereof is fixed in the upper part of the pressing tool, which is connected to the moving pressing ram. Reference is made to a lower part slider if the slider element receiving means thereof is connected to the lower pressing tool which is fixed on the rigid press table. Irrespective of the part to which the slider element receiving means of the wedge drive is connected, it usually has a linear guide means in which the movable slider element is reciprocatable, but as such it is fixedly connected to the slider element receiving means. The driver element is usually in the form of a rigid element fixedly connected to the part of the pressing tool, to which the slider element receiving means is not fastened. The driver element usually has inclined wedge portions and therewith serves as a drive element in relation to the movable slider element.
In the situation involving a substantially perpendicular advance movement of a pressing tool, which is referred to as the working stroke, the slider element which is in its rearward position comes to bear against the rigidly standing driver element and supported thereby is advanced by way of the inclined positioning thereof (wedge shape) facing in the working direction. In that situation the inclination of the linear guide means of the slider element receiving means is matched to the inclined positioning of the driver element so that no acceleration of the movable slider element is involved, in relation to the actual pressing speed. The movable slider element is thus only driven by the pressing tool and urged controlledly forwardly or outwardly in order to be able to perform the stamping or shaping work. In the rearward stroke movement in which the pressing tool has moved beyond its bottom dead center position and the two parts are moving away from each other again, the movable slider element is usually pushed back into its original position by means of a suitably designed resilient element, whereupon the procedure can be re-started. The return force required for the return movement of the slider element is usually between 2 and 10% of the actual working force and the weight of the slider element. In that respect, decisive aspects in regard to the magnitude of the pressing force are the dimensions of the surfaces for transmitting the pressure, which are referred to as sliding surfaces, the respective inclinations of the linear guide means in the slider element receiving means and the inclined positioning of the driver element as well as the co-operation of the surfaces and inclinations and the structure of the slider element itself. The pressures to be transmitted are usually between a few 100 kN and several 10,000 kN.
The linear guide means in the slider element receiving means was intended to guide the movable slider element with as little play as possible and in so doing to withstand high pressing forces and afford long service lives. To permit burr-free cutting or perforating of a workpiece a tolerance in terms of accuracy of movement of the movable slider element of a maximum of 0.02 mm is required. If that tolerance is not met, the workpieces which are cut or perforated or shaped in some other way can no longer be placed one upon the other in accurate register relationship so that errors in the basic bodywork structure occur and/or workpieces rubbing against each other means that faster corrosion occurs, the bodywork constructed is of reduced strength and possibly an increased amount of noise is generated by virtue of sheet metal parts which come loose. To avoid all those disadvantages, the requirement in particular in the automobile industry is that a wedge drive provides for extremely high levels of accuracy of movement and permanently withstands the pressing pressures required or makes them available in relation to the stamping or shaping tool.
In order to afford the required accuracy of movement here, various concepts have been developed, of which some are set forth hereinafter. By way of example slider guide means with side sliding plates and driver elements arranged at a right angle as well as a screwed cover plate for holding the slider element are known. Slider guide means of that kind admittedly withstand very high pressing forces and lateral thrust forces but they are very complicated and costly to manufacture as a high level of manual co-ordination complication and expenditure is required for matching the guide play between the elements. A further problem which has been found is inadequate protection in regard to the slider guide means falling apart, in which case the whole of the slider weight plus the rearward attachment forces act on the fastening screws of the cover plate and can very rapidly overload them. In addition such a slider guide means is comparatively large in structural size and is therefore unsuitable for constructing small sliders.
Slider guide means are also known having lateral angle bars and a driver plate arranged at a right angle. Unlike the above-discussed slider guide means the combination of the lateral sliding plates with a cover plate leads to a reduction in the amount of structural space required so that in particular it is also possible as a result to construct smaller slider sizes. It will be noted however that high forces act on the fastening screws of the angle bars and as a result provide that there is a relatively high risk of accident. In addition the complication and expenditure in terms of coordinating the co-operating elements for matching the guide play is high so that additional costs are also incurred here.
A further kind of slider guide which is used includes lateral sliding and cover plates which are inclined at an angle of 45°. They are therefore arranged approximately in a roof-shaped configuration. That makes it possible to achieve a reduction in structural width as the cover bars and the sliding plates are arranged one over the other and not one beside the other. It will be noted however that the structural space required is still very great so that it is scarcely possible to produce small sliders. In addition the traction forces occurring have a detrimental effect on the fastening screws of the cover plates, and that leads to a high level of process uncertainty.
A further known structure includes a slider guide means with a driver plate and one or two column guide means with bushes in order to hold the slider element laterally and to prevent it from dropping out. The use of a guide column with a driver plate means that admittedly only still comparatively small structural spaces are required and it is possible to achieve considerably less expensive manufacture than when using the above-mentioned solutions in the state of the art. It will be noted however that the column guide means, due to the type of structure involved, is not capable of compensating for high lateral pressures. In addition it cannot carry any heavyweight slider elements so that those slider elements produce less pressing forces and are more susceptible to trouble in the pressing procedure.
A further kind of slider element guide arrangement is known for example from EP 1 035 965 B1. This arrangement provides for a clamping embracing relationship in respect of the slider element guide means, wherein the driver element provides a prism guide and sliding plates are inserted between the driver element and the slider element. The roof shape involved means that very high slider forces are possible, while entailing small structural spaces, and equally a very accurate guide play so that the wedge drive or the slider element guide means is stable and has a long working life. It will be noted however that manufacture of the clamping guide means, because of the expensive cutting machining operations required to achieve a precise fitting shape, is really complicated and cost-intensive as a result.
Further wedge drives are also known for example from EP 1 259 371 B1, DE 198 60 178 C1 and EP 1 197 319 B1.
All the above-described design concepts of a slider element guide means for a wedge drive have one or more sliding plates for the transmission of generally high pressing forces, and likewise suitably designed holding elements for holding the slider element in the guide provided for same. The sliding plates serve to permanently transmit the working pressures exerted by the pressing tool from the slider element receiving means and the driver element to the movable slider element and thus to guarantee the actual advancing drive effect. The holding elements serve for linearly holding the slider element on the sliding plates of the sliding element receiving means, in which case they permanently ensure the required accuracy of movement and are intended to possibly compensate for lateral thrust forces which occur in the shaping operation or in the cutting or stamping procedure.
Now the object of the present invention is to further develop a wedge drive as set forth in the classifying portion of claim 1, in such a way that a guide for the movable slider element is provided, which permits still better motional accuracy than the solutions in the state of the art, which provides for optimum conversion of the pressing force which acts into the stamping or shaping movement, which compensates for lateral thrust forces even better than the state of the art and which provides a longer service life for the wedge drive than is hitherto possible with the solutions in the state of the art. The invention further seeks to provide that a lower level of complication and expenditure is required when coordinating the wedge drives and more economical manufacture becomes a possibility.
For a wedge drive as set forth in the classifying portion of claim 1 that object is attained in that a dovetail-like or prism guide means is provided between the slider element and the slider element receiving means. For a slider element for such a wedge drive the object of the invention is attained in that the slider element has a dovetail-like or prismatically shaped side. Further developments of the invention are defined in the appendant claims.
That therefore provides a wedge drive or cotter key in which the movable slider element has a dovetail-like or prismatic side, wherein the slider element receiving means is in the form of a corresponding counterpart portion so that the slider, element with its dovetail-like or prismatic side can engage into the slider element receiving means and can be guided and held therein. The surfaces on the slider element and/or the slider element receiving means, that are respectively provided by the dovetail shape and the prism shape, bear against each other, in which case forces directed in different directions can be carried without any problem by virtue of the surfaces which are at an angle relative to each other, in the dovetail or prism shape. The dovetail shape means that, after being inserted into the correspondingly shaped receiving configuration of the slider element receiving means, the movable slider element is safeguarded against falling out or lateral displacement, without further measures.
Advantageously sliding surfaces are provided on the slider elements and/or the slider element receiving means. In a particularly preferred feature the dovetail-like or prism guide means includes at least two sliding plates arranged at an angle relative to each other. Advantageously the sliding plates of the dovetail-like or prism guide means can be L-shaped in cross-section. It is further found to be advantageous if sliding plates are provided on all surfaces, which slide against each other, of the slider element and the slider element receiving means, so that in each case at least two sliding plates arranged at an angle relative to each other are provided on the slider element and the slider element receiving means. The sliding plates which are roof-shaped or L-shaped in cross-section can advantageously be so arranged that their inner narrow sides, by virtue of the outwardly inclined oblique positioning of the sliding plates, afford an undercut configuration in the form of the above-mentioned dovetail guide configuration.
By virtue of the provision of sliding plates at two sides of the slider element and the slider element receiving means respectively at the same time, wherein they are arranged symmetrically and in an L-shape or in a roof shape so that the shape of a dovetail guide means can be achieved, it is particularly advantageously possible to dispense with further, cost-intensive, linear holding elements. Furthermore, the manufacturing costs can be markedly reduced in comparison with the solutions in the state of the art as fewer components are provided than in the state of the art without in any way adversely affecting the mode of operation of the wedge drive but rather permitting more reliable and more secure operation without the provision of holding elements, but with an extremely high level of motion accuracy.
Advantageously the dovetail-like or prism guide means includes a positively locking connection between the slider element and the slider element receiving means. The provision of such a positively locking connection affords a compact unit, by way of which even high pressing forces can be transmitted without any problem. Furthermore that prevents the slider element and the slider element receiving means from unwantedly sliding out of each other as the positively locking relationship in the region of the dovetail or prism guide means and the mechanical contact between the two portions to be joined of the slider element and the slider element receiving means provides that the forces to be transmitted are in fact transmitted by way of the surfaces which are in contact with each other and which are at an angle relative to each other and in that respect assist with holding the component parts together, by virtue of their angular positioning.
It has further proven to be advantageous if the slider element receiving means is of a protruding configuration in the region of the sliding surfaces and/or the receiving means of the sliding plates. That provides a larger surface for the sliding movement of the slider element with respect to the slider element receiving means so that very good transmission of the pressing forces by way of those enlarged receiving surfaces is possible.
Advantageously the sliding plates can be releasably fixed to the slider element receiving means and/or the slider element, in particular by fixing screws. The releasability of the sliding plates from the slider element receiving means and the slider element respectively means that it is possible to replace them when wear occurs. It will be appreciated that in principle it would also be possible to equip the corresponding sliding surfaces of the slider element receiving means and the slider element in such a way that they can slide against each other, without the interposition of sliding plates. In that case however in the event of wear it would be necessary to replace the slider element receiving means and the slider element themselves so that it has proven to be less expensive and in operation easier in terms of handling if the arrangement has releasable sliding plates as then replacement thereof is possible quickly and without any problem.
The side of the slider element, which is of a dovetail-like or prismatic shape, advantageously has support surfaces as the sliding surfaces, in particular for the attachment of sliding plates. It has proven to be particularly advantageous in that respect to provide in each case two sliding plates which are arranged at an angle relative to each other as here it is possible to avoid arduous adjustment of four individual sliding plates which are arranged at an angle relative to each other. It is only necessary to implement adjustment at a respective one of the support surfaces for a respective sliding plate so that it is possible to rapidly change sliding plates.
Advantageously a wedge guide means is provided between the slider element and the driver element. That arrangement provides that very high forces can be carried while involving a comparatively small structural space, while at the same time accurate stable guidance for the slider element on the driver element upon movement thereof is possible.
Advantageously the wedge guide means includes two sliding plates arranged at an angle relative to each other. Those sliding plates advantageously comprise a material which assists with the sliding movement, in particular bronze with a solid lubricant. The provision of the sliding plates which are fastened in particular replaceably to the driver and/or slider element provides in a simple fashion that the plates can be replaced in the event of wear while in operation providing for optimum sliding movement of the surfaces, which are joined to each other, of the driver element and the slider element.
It has further proven to be advantageous if the dovetail-like or prism guide means and the wedge guide means are provided at an angle relative to each other on the slider element. The arrangement involving a plurality of angles relative to each other means that it is possible to reduce in particular the structural size of the wedge drive, thus affording a compact unit which can be used even with constricted space conditions within a pressing tool.
It is further found to be advantageous if the dovetail-like or prism guide means and the wedge guide means are provided at two mutually adjacent sides of the slider element. That makes it possible to improve the accuracy of movement but at the same time primarily also it is possible to reduce the structural size in comparison with the solutions in the state of the art which usually involve operative engagement on a driver element and operative engagement on the slider element receiving means at two mutually oppositely disposed sides of the slider element.
The slider element can have a third side adjacent to the other two sides, with a receiving means for receiving a processing tool. In that case the third side advantageously has at least two undercut configurations and/or grooves for the insertion of protruding elements of a receiving means for receiving a processing tool. The provision of such a separate receiving means for receiving a processing tool such as for example a perforating punch leads to simple replacement of the tool without any problem as it is only necessary for the receiving means to be removed from the third side of the slider element and replaced by another receiving means which for example carries a different tool. This totally eliminates a tedious procedure of screwing on and unscrewing the processing tool itself, possibly with drilling of further holes in the slider element. The provision of undercut configurations and/or grooves at the third side of the slider element means that the receiving means can be inserted there for example by being pushed into place, in which case further fixing is not even necessary as optimum transmission of force is already guaranteed in particular by virtue of the undercut configurations, due to the positively locking connection afforded thereby.
The third side of the slider element can also be provided with at least one wedge surface, in which case the receiving means then preferably has a corresponding wedge surface to provide a positively locking connection between the slider element and the receiving means for the processing tool. Lateral thrust forces can be carried thereby and the transmission of force can be optimized.
The mode of operation of a wedge drive usually comprises the working stroke and the return motion. During the working stroke the slider element is moved outwardly between the sliding surfaces, which are arranged in wedge form, of the driver element and the slider element receiving means, in which case the slider element receiving means and the driver element are movable towards each other perpendicularly, driven by the pressing stroke. The pressing force applied by the pressing tool corresponds in that respect to the counteracting force which the wedge drive applies for the work done by it, for example cutting, perforating or post-shaping a bodywork portion, wherein that is distributed to the sliding surfaces in dependence on the respective angular position of the individual sliding surfaces relative to each other. Due to the provision of sliding surfaces which are arranged at an angle relative to each other and which are arranged in a roof shape or a prism shape relative to each other, the movable slider element is automatically centered between the slider element receiving means and the driver element or on the sliding surfaces thereof. That can provide a very high level of motion accuracy and lateral guidance for the slider element, while manufacturing tolerances or other inaccuracies caused by manufacture can be compensated and thus no longer have an adverse influence.
In the return motion of the slider element, referred to as the rearward stroke, in which the pressing tool moves away from each other and thus the slider element receiving means is moved away from the driver element, the slider element is retracted into the region between the slider element receiving means and the driver element. The dovetail shape of the guide means between the slider element receiving means and the slider element once again permits self-centering linear guidance for the slider element. The forces acting on the slider element in the rearward stroke or in the return motion are restricted only by the weight of the slider element and the retraction forces acting on the slider element receiving means, the slider element and the driver element, as the pressing tool moves apart. The sliding surfaces of the slider element and the slider guide element, which run against each other in that situation, can be reduced in their dimensions in relation to the sliding surfaces which run against each other in the working stroke, so that the above-mentioned L-shape for the sliding surfaces on the dovetail guide means is found to be highly suitable in that respect.
In the case of a suspended upper part slider or wedge drive the weight of the slider element acts on the surfaces of the slider element receiving means, which bear in positively locking relationship against the slider element sliding surfaces of the dovetail guide arrangement, and exerts a downwardly directed spreading force on those surfaces of the sliding element receiving means. By virtue of the positively locking shoulder support for the slider element with respect to the slider element receiving means however those lateral thrust forces are compensated so that permanent and stable fixing of the slider element to the slider element receiving means and the sliding plates on the slider element and the slider element receiving means is possible. Therefore the fixing screws of the sliding plates are not subject to any forces such as to damage them, in particular tensile forces. As guidance for the slider element along the slider element receiving means by virtue of the dovetail guide arrangement is possible with a high degree of precision and without being sensitive to lateral thrust forces as well as being inexpensive to manufacture, without the provision of further components in the form of a linear guide means, the result is a compact wedge drive with a very high level of accuracy of motion, which is also insensitive in relation to manufacturing tolerances. As clamp guides or further elements are no longer required, not only can the costs be reduced in comparison with the solutions in the state of the art, but the process reliability is also increased and a possible risk of accident reduced. As the slider element only needs to be pushed into the slider element receiving means, assembly of the wedge drive is simplified in comparison with the solutions in the state of the art. It is possible to dispense with a cost-intensive operation of grinding in the guide elements as the prism guides or dovetail guide of the slider element receiving means, the slider element and the driver element are insensitive in relation to tolerances in manufacture. The self-centering effect achieved by the prism guides also leads to a very high level of accuracy in terms of motion in regard to carrying lateral thrust forces. By virtue of the compact structure of the wedge drive it is not only suitable for a small structural space available within a pressing tool, but, as will be appreciated, it is also suitable for uses involving larger dimensions. The prism guide means or the dovetail-like guide means provided between the slider element and the slider element receiving means can thus be used to equip small, medium and large-format wedge drives, thus affording a large range of uses.